Astronomy explained upon Sir Isaac Newton's principles. And made easy to those who have not studied mathematics / To which are added, a plain method of finding the distances of all the planets from the sun, by the transit of Venus over the sun's disc, in the year 1761. An account of Mr. Horrox's observation of the transit of Venus in the year 1639; and, of the distances of all the planets from the sun, as deduced from observations of the transit in the year 1761. By James Ferguson.

James Ferguson

Date:: 1770

Credit: Astronomy explained upon Sir Isaac Newton's principles. And made easy to those who have not studied mathematics / To which are added, a plain method of finding the distances of all the planets from the sun, by the transit of Venus over the sun's disc, in the year 1761. An account of Mr. Horrox's observation of the transit of Venus in the year 1639; and, of the distances of all the planets from the sun, as deduced from observations of the transit in the year 1761. By James Ferguson. Source: Wellcome Collection.

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$this Circle.is one of 24 hours divided into their re- fpective Halves and Quarters. 2. A moving el- liptical. Plate, painted blue, to reprefent the rifing of the Tides under and oppofite to the Moon; and has the words, High Water, Tide falling, Low Water, Tide rifing, marked upon it. To one end of this Plate is fixed the Moon M by the Wire W, and goes along with it. 3. Above this elliptical Plate is a round one, with the Points of the Com- pafs upon it, and alfo the names of above 200 places in the large Machine.(but only. 32 in the Figure, to avoid confufion) fet over thofe Points on which the Moon bears when fhe raifes the Tides to ‘the greateft heights at thefe Places twice in every lunar day: and to the North and South Points of this Plate are fixed two Indexes J and K, which fhew the times of High Water, in the Hour-Circle, at all thefe places. 4. Below the elliptical Plate are four {mall Plates, two of which project out from below ening the Ellipfe, fhew the Spring Tides, which are then raifed to the greateft heights by the united other two of thefe fmall Plates appear at low water when the Moon is in her Quadratures, or at the fides of the elliptic Plate, to thew the Neap Tides,; the Sun and Moon then acting crofs-wife to each other. Whenany two of thefe {mall Plates appear, the other two are hid; and when. the Moon is-in her Octants, they all difappear, there being neither Spring nor Neap Tides at thofe times. Within the Box are a tew Wheels for performing thefe Motions by the Handle or Winch H. Turn the Handle until the Moon M comes ta any given day of her age in the Circle of 29% equal parts, and the Moon’s Wire W will cut the time ef her coming to the Meridian on that day, in the Hour-Circle ;. the X]lf-under the Sun being Mid- -day, and the oppofite XII mid-night: then looking _ for the name of any given place on the round Plate . 3 | (which$

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